Tendon ruptures constitute a major part of musculoskeletal injuries, with Achilles tendon ruptures as one of the most frequently ruptured tendons in the human body.[1] Functional loss of the repaired tendons is due to two major drawbacks, (i) adhesion formation to the surrounding tissue, resulting in a reduced range of motion and (ii) insufficient mechanical strength acquired during initial tendon healing, leading to re-rupture.[1] Due to limited tendon vascularity and innervation, the natural healing of the tendon is inefficient[2] and therapeutic repair options include autografts, allografts, xenografts, suture techniques and tendon prostheses.[3]
A regenerative engineering approach addressing the major drawbacks in Achilles tendon rupture, has been explored before by developing a reversibly expandable electrospun polymer tube, made from a biodegradable co-block polymer, a polyester urethane named DegraPol® (DP)[4], see also WO 2013/026937 A1. Electrospun tube made of a newly synthesized type of DP, which is softer and more elastic, surgeon friendly and better suited for tendon rupture repair[4], compared to the already established classic DP[5] has been applied over the wound site after conventional tendon repair. It has been shown that is does not evoke an adverse cellular response and that it significantly minimized peritendinous adhesion formation in a rabbit model.[6] Using this newly synthesized DP for production of reversibly expendable electrospun scaffolds/tubes offers a big advantage over other electrospun polymers like poly(lactide-co-glycolic acid) (PLGA) or poly(caprolactone) (PCL), that exhibit considerably low strain at break.[7]
To address the issue of insufficient strength at the tendon rupture repair site and to further develop the elastic DP tube as an implant for tendon rupture repair, it has been explored as a carrier system for growth factor(s), more specifically platelet-derived growth factor-BB (PDGF-BB). This approach aims to provide a bioactive scaffold that can locally promote and accelerate tendon healing. Administration of biological molecules like growth factors has been proposed and studied in aiding the recapitulation of the native tendon function after injury.[8] More specifically, PDGF-BB has been shown to affect matrix remodeling, increase collagen synthesis and cell proliferation[9], thus its local delivery might also affect the biomechanical strength of the repaired tendons.